The present invention relates to a novel organopolysiloxane compound having at least one .alpha.-substituted or unsubstituted benzoin group expressed by the formula ##STR2## where Ph is a phenyl group and R is a hydrogen atom or an alkyl group, bonded to the silicon atom in a molecule of the organopolysiloxane and a method for the preparation thereof.
There have been known several organosilane compounds of silyl esters having one benzoin group of the above formula bonded to the silicon atom of an organosilane compound (see, for example, U.S. Pat. No. 3,636,026) but no organopolysiloxane compounds having the benzoin group are hitherto known.